Terminal, base station apparatus, communication method, and apparatus

ABSTRACT

A terminal is disclosed that includes a processor, coupled to a transceiver, that monitors a PDCCH (Physical downlink control channel) candidate in a first search space during a random access procedure. The transceiver receives a random access response or a PDSCH (Physical downlink shared channel) for contention resolution from a base station, based on information included in the PDCCH candidate. The transceiver receives a PDSCH or transmits an uplink signal based on information included in a PDCCH candidate monitored in the first search space, until a second search space of a type other than the first search space is configured after the random access procedure is completed. In other aspects, a base station, a communication method, and an apparatus are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application and, thereby, claimsbenefit under 35 U.S.C. § 120 to U.S. patent application Ser. No.17/051,024, filed on Oct. 27, 2020, titled “TERMINAL AND BASE STATIONAPPARATUS,” which is a national stage application of PCT Application No.PCT/JP2018/018825, filed on May 15, 2018. The contents of theseapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a user device and a base stationapparatus in a radio communication system.

BACKGROUND ART

At present, in 3GPP (Third Generation Partnership Project), developmentof a radio communication system has been in progress, which is referredto as an NR (New Radio), in order to realize further enlargement of asystem capacity, further increase of a data transmission speed, andfurther reduction of a delay in a radio communication section. (Thisradio communication system may be referred to hereinafter as 5G or NR.)In 5G, various techniques of radio communication have been discussed tosatisfy requirements of obtaining a throughput of 10 Gbps or more andkeeping a delay in a radio communication section equal to or less than 1ms.

In NR, a user device performs cell detection and cell identification byuse of a synchronization signal transmitted by a base station apparatus,and obtains part of system information required for an initial access,in the initial access at the time of establishing connection between theuser device and the base station apparatus (for example, see Non-PatentDocument 1).

Also, in NR, it is expected to use a wide frequency range, from a lowfrequency band similar to that for the LTE (Long Term Evolution) to ahigher frequency band than that for the LTE. As a transmission lossincreases in the high frequency band, it is considered to applybeamforming with a small beam width to compensate for the transmissionloss (for example, see Non-Patent Document 2).

RELATED-ART DOCUMENTS Non-Patent Document

-   Non-Patent Document 1: 3GPP TS 38.213 V15.1.0 (2018-03)-   Non-Patent Document 2: 3GPP TS 38.211 V15.1.0 (2018-03)

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In NR, plural types are defined for search spaces as sets of PDCCH(Physical downlink control channel) candidates to be monitored by a userdevice. However, it has not been clear which type of search space ismonitored by the user device, and it has not been clear when such asearch space is monitored by the user device.

The present invention has been made in view of the above-describedproblem, and an object of a user device is to identify a search spacefor use in the random access procedure in the NR, and perform monitoringefficiently.

Means to Solve the Problem

According to a disclosed technique, a user device for communicating witha base station apparatus is provided, and includes a receiving unitconfigured to receive a DL (Downlink) signal included in a search spaceas a set of candidates of a PDCCH (Physical downlink control channel)from the base station apparatus, a control unit configured to monitorfor obtaining a PDCCH candidate addressed to the user device based on avalid period defined for the search space, and a communication unitconfigured to receive a PDSCH (Physical downlink shared channel) ortransmit a UL (Uplink) signal to the base station apparatus, based oninformation included in the PDCCH candidate addressed to the userdevice.

Advantage of the Invention

According to the disclosed technique, an object of a user device is toidentify a search space for use in the random access procedure in theNR, and perform monitoring efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a configuration example of a radiocommunication system in an embodiment of the present invention.

FIG. 2 is a sequence view for describing an example of a random accessprocedure in the embodiment of the present invention.

FIG. 3 is a flowchart for describing an example of the random accessprocedure in the embodiment of the present invention.

FIG. 4 is a view illustrating one example of a functional configurationof a base station apparatus 100 in the embodiment of the presentinvention.

FIG. 5 is a view illustrating one example of a functional configurationof a user device 200 in the embodiment of the present invention.

FIG. 6 is a view illustrating one example of a hardware configuration ofthe base station apparatus 100 or the user device 200 in the embodimentof the present invention.

MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is described below by referringto the drawings. Note that the embodiment described below is only oneexample, and the embodiment to which the present invention is applied isnot limited to the following embodiment.

For the operation of a radio communication system of the embodiment ofthe present invention, existing techniques are used suitably. However,those existing techniques are, for example, the existing LTE, but arenot limited to the existing LTE. The term “LTE” used in the presentspecification should be read to have a broad meaning inclusive ofLIE-Advanced and systems later than LIE-Advanced (for example, NR or5G), unless otherwise mentioned.

In the embodiment of the present invention to be described hereinafter,terms used in the existing LTE are used, including SS (SynchronizationSignal), PSS (Primary SS), SSS (Secondary SS), PBCH (Physical broadcastchannel), PRACH (Physical RACH), DL (Downlink), UL (Uplink) and thelike. Those are for the convenience in the description. Signals,functions and the like similar to those may be referred to with othernames.

In the embodiment of the present invention, duplex systems may be a TDD(Time Division Duplex) system, FDD (Frequency Division Duplex) system,or others (for example, Flexible Duplex or the like).

In the description below, transmitting a signal with a transmission beammay be transmission of the signal multiplied by a precoding vector(precoded by the precoding vector). Similarly, receiving a signal with areception beam may be multiplication of the received signal by apredetermined weight vector. Also, transmitting a signal with atransmission beam may be expressed as transmission of the signal througha particular antenna port. Similarly, receiving a signal with areception beam may be expressed as reception of the signal through aparticular antenna port. The term of antenna port means a logicalantenna port as defined in 3GPP standards or a physical antenna port.

Methods of forming a transmission beam and reception beam are notlimited to those methods described above. For example, a method ofchanging an angle of each antenna in a base station apparatus 100 or auser device 200 having plural antennas may be applied. A method ofcombining a method of using a precoding vector and a method of changingthe angle of the antenna may be applied. Different antenna panels may beswitched and utilized. A method of combining methods of using pluralcombined antenna panels may be applied. Other methods may be applied.Also, plural transmission beams different from one another may be usedin, for example, a high frequency band. Using plural transmission beamsis referred to as multi-beam operation. Using a single transmission beamis referred to as single beam operation.

In the embodiment of the present invention, “being configured” of awireless parameter or the like may be being pre-configured or beingpredetermined of a prescribed value, or may be being configured of awireless parameter notified by the base station apparatus 100 or theuser device 200.

FIG. 1 is a diagram illustrating a configuration example of a radiocommunication system in the embodiment of the present invention. Asillustrated in FIG. 1, the radio communication system in the embodimentof the present invention includes the base station apparatus 100 and theuser device 200. In FIG. 1, the base station apparatus 100 and the userdevice 200 are illustrated respectively singly. However, these areexamples. The base station apparatus 100 and the user device 200 may berespectively plural devices.

The base station apparatus 100 is a communication device which providesone or more NR cells, and communicates with the user device 200wirelessly. The base station apparatus 100 transmits a synchronizationsignal and system information to the user device 200. For example, thesynchronization signal is NR-PSS and NR-SSS. The system information istransmitted, for example, by an NR-PBCH. Also, the system information isreferred to as notification information. Both of the base stationapparatus 100 and the user device 200 can transmit and receive a signalby performing beamforming. The user device 200 is a communication devicehaving a radio communication function, such as a smartphone, mobilephone, tablet, wearable terminal, M2M (Machine-to-Machine) communicationmodule, and the like, and wirelessly connects to the base stationapparatus 100, and utilizes various communication services provided bythe radio communication system. In the step of the initial access, theuser device 200 transmits a preamble signal of random access to the basestation apparatus 100. This random access is performed on the basis ofRMSI (Remaining minimum system information) that is system informationaccording to an NR-PDSCH (Physical downlink shared channel) which isscheduled by an NR-PDCCH (Physical downlink control channel), inaddition to the system information according to the NR-PBCH receivedfrom the base station apparatus 100. For example, the RMSI includesinformation required for initial access, such as RACH configuration andthe like.

As illustrated in FIG. 1, the base station apparatus 100 transmits a DLsignal inclusive of the control information to the user device 200through the PDCCH. In the initial access, the user device 200 performsmonitoring based on a search space for the random access in relation tothe DL signal. The search space for the random access, for example,includes a PDCCH for scheduling a message 2 as a random access responseand a message 4 for resolution of contention. This user device 200receives a PDSCH to be scheduled in this PDCCH. The search space for therandom access includes, for example, a PDCCH corresponding to schedulinga UL signal for retransmitting a message 3. The user device 200retransmits the message 3 on the basis of scheduling of this PDCCH.

A set of PDCCH candidates to be monitored by the user device 200 aredefined as a set of a search space. The set of the PDCCH search space isa set of a common search space or a set of a UE-specific search space.The user device 200 monitors the PDCCH candidates from the set of one orplural search spaces. The base station apparatus 100 locates a PDCCH fora certain user device 200 in the PDCCH search space, and transmits asignal including the PDCCH located in this PDCCH search space to theuser device 200.

A search space for random access may be defined as “Type-1 PDCCH commonsearch space”. Contents of the “Type-1 PDCCH common search space” may benotified to the user device 200 by information element “ra-SearchSpace”included in RRC (Radio Resource Control) signaling, or may bepredetermined.

For example, the PDCCH scheduling the message 2 as a random accessresponse is scrambled in CRC (Cyclic redundancy check) scramble with anRA-RNTI (Random Access—Radio Network Temporary Identifier). Also, forexample, the PDCCH scheduling retransmission of the message 3 isscrambled in CRC scramble with a Temporary C-RNTI (Cell-RNTI). Also, forexample, the message 4 for performing contention resolution is scrambledin CRC scramble with the Temporary C-RNTI or C-RNTI. In a search space,the user device 200 monitors the control information scrambled in CRCscramble as described above.

It is noted that a message 1 as a random access preamble does not needto be triggered in a search space for the random access. For example,the message 1 may be triggered by RRC signaling. Also, the message 1 maybe triggered, for example, by the user device 200. Also, the message 1may be triggered, for example, by control information through the PDCCHfrom the network. In relation to this PDCCH, the user device 200 maymonitor the common search spaces of other types or UE-specific searchspace.

FIG. 2 is a sequence diagram for describing an example of a randomaccess sequence in the embodiment of the present invention. FIG. 2illustrates an example of procedure of contention-based random access.In the case of the contention-based random access, a preamble for use atrandom is selected from a preamble index of a predetermined range.

In a step S1, the user device 200 transmits a random access preamble(message 1) to the base station apparatus 100 on the basis ofinformation which has been obtained previously from the base stationapparatus 100 for identifying RACH resources and the preamble index.

In a step S2, the base station apparatus 100 transmits a random accessresponse (message 2) to the user device 200. The random access responseis a response to the random access preamble, and is transmitted to theRA-RNTI through the PDCCH, and includes at least an identifier, timingalignment and initial uplink grant of the random access preamble. In acase of contention-free random access, the random access procedure isterminated in the step S2. In a case of contention-based random access,the flow proceeds to a step S3. In the step S2, the user device 200monitors a search space for receiving a random access response.

In the step S3, the user device 200 performs the scheduled ULtransmission (message 3) to the base station apparatus 100 on the basisof the initial uplink grant included in the random access responsereceived in the step S2. If the message 3 has not been normally receivedin the base station apparatus 100, scheduling corresponding toinstruction for retransmitting the message 3 is transmitted to the userdevice 200 through the PDCCH. The user device 200 monitors the searchspace to receive this PDCCH.

In a step S4, at the base station apparatus 100, schedulingcorresponding to information for resolving contention is transmitted tothe user device 200 through the PDCCH. The user device 200 monitors asearch space for receiving this PDCCH. If the resolution of contentionis successful according to the information for contention resolution,the user device 200 terminates the random access procedure as the randomaccess has been regarded as successful.

FIG. 3 is a flowchart for describing an example of the random accessprocedure in the embodiment of the present invention. FIG. 3 is a viewillustrating one example of contention-based random access procedure. Atthe time of staring the random access procedure, “1” is set in atransmission counter.

In a step S11, the user device 200 selects a resource for use in therandom access procedure on the basis of information identifying aresource for performing the random access procedure received from thebase station apparatus 100, namely, information identifying the preambleformat, RACH resource and the like identified by the frequency regionand time domain. Then the user device 200 transmits a random accesspreamble (message 1) to the base station apparatus 100 by use of theselected resource (S12).

In a step S13, the base station apparatus 100 transmits a random accessresponse (message 2) to the user device 200. The random access responseis a response to the random access preamble, and transmitted to theRA-RNTI at the PDCCH. The PDSCH scheduled by this PDCCH includes atleast an identifier of the random access preamble, timing alignment,initial uplink grant and temporary C-RNTI. The user device 200 monitorsthe search space for receiving the random access response. If the randomaccess response is received by the user device 200 (yes in S13), theflow proceeds to a step S14. If no random access response is received bythe user device 200 (no in S13), the flow proceeds to a step S16. If themessage 3 has not been normally received in the base station apparatus100, scheduling corresponding to the instruction for retransmitting themessage 3 is transmitted to the user device 200 through the PDCCH. Theuser device 200 monitors the search space to receive this PDCCH.

In the step S14, the user device 200 performs uplink transmission(message 3) on the basis of the uplink grant included in the randomaccess response. In the uplink transmission, information, whichrepresents at least an RRC connection request and NAS (Non-AccessStratum) UE (User Equipment) identifier, is transmitted. Then the PDSCH,which is transmitted by the base station apparatus 100 to the userdevice 200 at the temporary C-RNTI or C-RNTI through the PDCCH asresolution of contention (contention resolution, message 4) and isscheduled through the PDCCH, includes at least control information forestablishing RRC connection and a predetermined MAC (Medium AccessControl) control element transmitted by the user device 200 in the stepS14. This MAC control element is used for resolving contention. The userdevice 200 monitors a search space for receiving the PDCCH schedulingthe PDSCH including the message 4. It is noted that contentionresolution (step S14) may be performed at the time of performing thecontention-based random access, and may not be performed at the time ofperforming the contention-free random access. The user device 200, ifthis MAC control element coincides with part of or all of the datatransmitted in the step S14 (yes in S14), proceeds to a step S15, and ina case of non-coincidence (no in S14), proceeds to the step S16.

In the step S15, the user device 200 recognizes that the random accessis successful. In the use of the temporary C-RNTI, the temporary C-RNTIis made a C-RNTI, to terminate the random access procedure.

In the step S16, the user device 200 determines whether the value of thetransmission counter has exceeded a notified or predetermined upperlimit. If it has exceeded the upper limit (yes in S16), the flowproceeds to a step S17. If it has not exceeded the upper limit (no inS16), the flow proceeds to a step S18.

In the step S17, the user device 200 recognizes that the random accessis unsuccessful, and terminates the random access procedure. On theother hand, in the step S18, the user device 200 increments thetransmission counter by one, returns to the step S11 for retransmittingthe random access preamble, and selects random access resources again.

As described above, the user device 200 in the random access proceduremonitors the search space for random access, namely the Type-1 PDCCHcommon search space. However, PDCCH candidates may be monitoredunnecessarily if the user device 200 always monitors the Type-1 PDCCHcommon search space. There is a limit in the number of PDCCH candidatesthat can be monitored by the user device 200. Thus, resources to beconsumed increase if the user device 200 always monitors the Type-1PDCCH common search space, so that influence occurs to monitoring ofother types of search space.

In view of this, a time domain for monitoring the search space forrandom access, namely the Type-1 PDCCH common search space, is limited,so that the user device 200 can perform monitoring the search space withgood efficiency. To be specific, the user device 200 can monitor thesearch space on the basis of a valid period defined for the searchspace. To this end, the base station apparatus 100 locates the PDCCHaddressed to a certain user device 200 to be included in this searchspace on the basis of the valid period defined for the search space, totransmit the PDCCH to the same user device 200.

The point at which the user device 200 starts monitoring of the Type-1PDCCH common search space is defined to be any one of the followingpoints.

1. Starting point of a RAR (random access response) window for receivingthe message 2

2. Transmission point of the message 1

3. Starting point of monitoring the PDCCH corresponding to the message 2

The point at which the user device 200 terminates monitoring of theType-1 PDCCH common search space is defined to be any one of thefollowing points.

4. Completing point of the random access procedure

5. Completing point of reception of the message 4

6. Completing point of resolution of contention with the message 4.

In relation to the starting points 1., 2. or 3. of monitoring of theType-1 PDCCH common search space, and the terminating points 4., 5. or6. of monitoring of the Type-1 PDCCH common search space, it is possibleto identify a time domain for monitoring of the Type-1 PDCCH commonsearch space according to any one of combinations of those points.

Furthermore, the monitoring may be defined, for example, in the mannerof 7. below.

7. The user device 200 uses the Type-1 PDCCH common search space onlyfor a case of monitoring the PDCCH for scheduling the message 2,scheduling instruction for retransmission of the message 3, orscheduling the message 4.

Also, for example, the Type-1 PDCCH common search space may be used forany of the cases of the above-described 1.-7. in order that the userdevice 200 monitors a PDCCH to be received after receiving the message 4until search spaces of other types are configured in the user device200. Also, the Type-1 PDCCH common search space may be used for any ofthe cases of the above-described 1.-7. in order that the user device 200monitors a PDCCH to be received after terminating a random accessprocedure until a search space of another type is configured in the userdevice 200.

For example, the operation of the user device 200 may be determined instandardization specification as follows.

A determination example of standardization specification: the userdevice 200 monitors the Type-1 PDCCH common search space only in a termfrom starting of the RAR window until terminating of the random accessprocedure.

According to the above-described embodiment, the user device 200 in arandom access procedure can perform monitoring of the search spaceefficiently by identifying a search space in a time domain, inclusive ofPDCCH candidates received from the base station apparatus 100. Also, theuser device 200 can perform monitoring of the search space efficientlyby using a search space of a particular type, only while a PDCCHscheduling a particular message is received.

In short, the user device can identify a search space for use in therandom access procedure in the NR, and perform monitoring efficiently.

(Device Configuration)

An example of a functional arrangement of the base station apparatus 100and the user device 200 for performing tasks and operations describedheretofore is described next. The base station apparatus 100 and theuser device 200 include functions for executing the above-describedembodiment. However, each of the base station apparatus 100 and the userdevice 200 may include only functions of part of the embodiment.

<Base Station Apparatus 100>

FIG. 4 is a view illustrating one example of a functional arrangement ofthe base station apparatus 100. As illustrated in FIG. 4, the basestation apparatus 100 includes a transmission unit 110, a reception unit120, a configuration information management unit 130 and an initialaccess configuration unit 140. The functional arrangement illustrated inFIG. 4 is only one example. Division of the functions and names offunctional components can be determined optionally so that tasks relatedto the embodiment of the present invention can be performed.

The transmission unit 110 includes a function for generating a signal totransmit to the side of the user device 200, and for transmitting thissignal wirelessly. The reception unit 120 has a function for receivingvarious types of signals transmitted by the user device 200, andobtaining information from the received signals, for example,information of a higher layer. Also, the transmission unit 110 has afunction for transmitting NR-PSS, NR-SSS, NR-PBCH and DL/UL controlsignals and the like to the user device 200. For example, thetransmission unit 110 transmits UL scheduling or notificationinformation to the user device 200, the notification informationincluding information for use in the initial access. The reception unit120 has a function of receiving a RACH preamble from the user device200.

The configuration information management unit 130 stores predeterminedconfiguration information, and various items of configurationinformation to be transmitted to the user device 200. Contents of theconfiguration information are, for example, information related totransmission/reception parameters for initial access or the like.

The initial access configuration unit 140 as described in the embodimentnotifies the user device 200 of information to be used in the initialaccess, and performs processing at the time of receiving the randomaccess preamble transmitted from the user device 200, transmission ofthe random access response, and the like. Also, the initial accessconfiguration unit 140 locates a PDCCH to be transmitted to the userdevice 200 in a predetermined search space, such as the Type-1 PDCCHcommon search space.

<User Device 200>

FIG. 5 is a view illustrating one example of a functional arrangement ofthe user device 200. As illustrated in FIG. 5, the user device 200includes a transmission unit 210, a reception unit 220, a configurationinformation management unit 230 and an initial access control unit 240.The functional arrangement illustrated in FIG. 5 is only one example.Division of the functions and names of functional components can bedetermined optionally so that tasks related to the embodiment of thepresent invention can be performed.

The transmission unit 210 generates a signal for transmission from datafor transmission, and wirelessly transmits this signal for transmission.The reception unit 220 wirelessly receives various signals, and obtainssignals of upper layers from the received signals of the physical layer.Also, the reception unit 220 has functions for receiving NR-PSS, NR-SSS,NR-PBCH, DL/UL control signals or the like transmitted by the basestation apparatus 100. The transmission unit 210 has, for example,functions for transmitting NR-PRACH, NR-PUSCH and the like to the basestation apparatus 100.

The configuration information management unit 230 stores various itemsof the configuration information received by the reception unit 220 fromthe base station apparatus 100 or the user device 200. Also, theconfiguration information management unit 230 stores predeterminedconfiguration information. Contents of the configuration informationare, for example, information related to transmission/receptionparameters for initial access or the like.

The initial access control unit 240, as described in the embodiment,generates a preamble and message related to the initial access to betransmitted from the user device 200 to the base station apparatus 100.Also, the initial access control unit 240 obtains a PDCCH address to thesame user device by monitoring a predetermined search space, such as theType-1 PDCCH common search space. Functional components related tosignal transmission in the initial access control unit 240 may beincluded in the transmission unit 210. Functional components related tosignal reception in the initial access control unit 240 may be includedin the reception unit 220.

<Hardware Configuration>

The views for the functional arrangement (FIGS. 4 and 5) used fordescribing the above-described embodiment of the present inventionillustrate blocks in units of functions. These functional blocks(components) are implemented by any combination of hardware and/orsoftware. Furthermore, means for implementing each functional block isnot particularly limited. Namely, each functional block may beimplemented by a single device with plural elements that are physicallyand/or logically coupled, or may be implemented by plural devicesobtained by directly and/or indirectly (e.g., by wire and/or wirelessly)connecting the two or more devices separated physically and/orlogically.

For example, the base station apparatus 100 and the user device 200 inone embodiment of the present invention may function as computers forperforming processes related to the embodiment according to the presentinvention. FIG. 6 is a diagram illustrating one example of a hardwareconfiguration of a radio communication device being the base stationapparatus 100 or the user device 200 according to the embodiment of thepresent invention. Each of the base station apparatus 100 and the userdevice 200 described above can be configured physically as a computerdevice including a processor 1001, a storage device 1002, an auxiliarystorage device 1003, a communication device 1004, an input device 1005,an output device 1006, a bus 1007 and the like.

Note that, in the following description, the term “apparatus” may bereplaced with a circuit, device, unit and the like. The hardwareconfiguration of the base station apparatus 100 and the user device 200may be configured to include one or more of the respective devicesillustrated in the figures and denoted at 1001-1006, or may beconfigured without including a part of the devices.

The respective functions in the base station apparatus 100 and the userdevice 200 are realized by reading predetermined software (programs) onhardware such as the processor 1001, the storage device 1002 and thelike, performing calculation in the processor 1001, and controllingcommunication in the communication device 1004 and reading and/orwriting of data in the storage device 1002 and the auxiliary storagedevice 1003.

For example, the processor 1001 causes an Operating System to operate soas to control the entire computer. The processor 1001 may be formed of acentral processing unit (CPU: Central Processing Unit) including aninterface with a peripheral device, control device, arithmetic unit,register, and the like.

Furthermore, the processor 1001 reads a program (program code), softwaremodule, or data from the auxiliary storage device 1003 and/or thecommunication device 1004 to the storage device 1002, and executesvarious processes in accordance with these. As the program, a program isused that is for causing a computer to execute at least a part of theoperation described in the embodiment above. For example, thetransmission unit 110, the reception unit 120, the configurationinformation management unit 130 and the initial access configurationunit 140 in the base station apparatus 100 illustrated in FIG. 4 may beimplemented by a control program stored in the storage device 1002 andexecuted by the processor 1001. Also, for example, the transmission unit210, the reception unit 220, the configuration information managementunit 230 and the initial access control unit 240 in the user device 200illustrated in FIG. 5 may be implemented by a control program stored inthe storage device 1002 and executed by the processor 1001. It isdescribed that the above-described various processes are performed bythe single processor 1001, but they may be simultaneously orsequentially performed by two or more processors 1001. The processor1001 may be implemented by one or more chips. Note that the program maybe transmitted from a network through an electrical communication line.

The storage device 1002 is a computer readable recording medium, and maybe formed of, for example, at least one of a ROM (Read Only Memory),EPROM (Erasable Programmable ROM), EEPROM (Electrically ErasableProgrammable ROM), RAM (Random Access Memory) and the like. The storagedevice 1002 may be referred to as a register, cache, main memory (mainstorage device) and the like. The storage device 1002 can store aprogram (program code), a software module and the like executable forperforming processing according to one embodiment of the presentinvention.

The auxiliary storage device 1003 is a computer readable recordingmedium, and can be formed of, for example, at least one of an opticaldisc such as a CD-ROM (Compact Disc ROM), hard disk drive, flexibledisc, magneto-optical disk (for example, compact disk, digital versatiledisk, and Blu-ray (registered trademark) disk), smart card, flash memory(e.g., card, stick and key drive), floppy (registered trademark) disk,magnetic strip, and the like. The auxiliary storage device 1003 may bereferred to as an auxiliary storage device. The above-described storagemedium may be, for example, a database, server, or any other appropriatemedium, including the storage device 1002 and/or the auxiliary storagedevice 1003.

The communication device 1004 is hardware (transmission/receptiondevice) for executing communication between computers through a wiredand/or wireless network, and is also referred to as, for example, anetwork device, network controller, network card, communication module,and the like. For example, the transmission unit 110 and the receptionunit 120 in the base station apparatus 100 may be implemented by thecommunication device 1004. Also, the transmission unit 210 and thereception unit 220 in the user device 200 may be implemented by thecommunication device 1004.

The input device 1005 is an input device for receiving an input from theoutside (e.g., a keyboard, mouse, microphone, switch, button, sensor andthe like). The output device 1006 is an output device for implementingan output to the outside (e.g., a display, speaker, LED lamp and thelike). Note that the input device 1005 and the output device 1006 may beconfigured to be integrated (for example, a touch panel).

Furthermore, the respective devices, such as the processor 1001 and thestorage device 1002, are connected by the bus 1007 for communication ofinformation. The bus 1007 may be formed of a single bus, or may beformed of different buses among the devices.

Furthermore, the base station apparatus 100 and the user device 200 maybe constituted to include hardware, such as a microprocessor, digitalsignal processor (DSP: Digital Signal Processor), ASIC (ApplicationSpecific Integrated Circuit), PLD (Programmable Logic Device), FPGA(Field Programmable Gate Array), and the like. By the hardware, a partof or all of the functional blocks may be implemented. For example, theprocessor 1001 may be implemented by at least one of these hardwarecomponents.

Conclusion of the Embodiment

As has been described heretofore, according to the embodiment of thepresent invention, a user device for communicating with a base stationapparatus is provided, comprising a receiving unit configured to receivea DL (Downlink) signal included in a search space as a set of candidatesof a PDCCH (Physical downlink control channel) from the base stationapparatus, a control unit configured to monitor for obtaining a PDCCHcandidate addressed to the user device based on a valid period definedfor the search space, and a communication unit configured to receive aPDSCH (Physical downlink shared channel) or transmit a UL (Uplink)signal to the base station apparatus, based on information included inthe PDCCH candidate addressed to the user device.

Owing to the configuration described above, the user device 200 canperform monitoring of a search space efficiently by identifying thesearch space in a time domain inclusive of PDCCH candidates receivedfrom the base station apparatus 100 in a random access procedure.Namely, the user device can perform monitoring efficiently byidentifying the search space used in the random access procedure in theNR.

The valid period defined for the search space may be a term in which arandom access procedure is executed. Owing to this configuration,monitoring of the search space can be performed efficiently as the userdevice 200 uses the search space of a predetermined type only when aPDCCH for scheduling a particular message is received.

A starting point of the valid period defined for the search space may beany one of a starting point of a window for receiving a random accessresponse, a transmission point of a random access preamble, or astarting point of monitoring a PDCCH corresponding to the random accessresponse. Owing to this configuration, the user device 200 can identifythe starting point of the search space.

A terminating point of the valid period defined for the search space isany one of a completing point of the random access procedure, acompleting point of reception of a message 4 for resolution ofcontention, or a completing point of resolution of contention with themessage 4. Owing to this configuration, the user device 200 can identifythe terminating point of the search space.

After terminating the random access procedure, monitoring for obtaininga PDCCH candidate addressed to the user device may be performed by useof the search space during a term until a search space of a type otherthan the search space is configured. Owing to this configuration, theuser device 200 can transmit and receive data by identifying the searchspace for use after terminating the random access procedure.

Also, according to an embodiment of the present invention, a basestation apparatus for communicating with a user device is provided,comprising a transmission unit configured to transmit a DL (Downlink)signal included in a search space as a set of candidates of a PDCCH(Physical downlink control channel) to the user device, a configurationunit configured to locate a PDCCH candidate addressed to the basestation apparatus in the search space based on a valid period definedfor the search space, and a receiving unit configured to receive a UL(Uplink) signal transmitted from the user device based on informationincluded in the PDCCH candidate addressed to the base station apparatus.

According to the above-described embodiment, the base station apparatus100 can identify a search space in a time domain, inclusive of PDCCHcandidates in a random access procedure, and locate the search space inthe PDCCH so as to perform monitoring of the search space efficiently.In short, the user device can identify a search space for use in therandom access procedure in the NR, and perform monitoring efficiently.

Supplement to the Embodiment

The embodiment of the present invention has been described above;however, the disclosed invention is not limited to the embodiment, and aperson ordinarily skilled in the art will appreciate various variations,modifications, alternatives, replacements and the like. Specificexamples of numerical values are used in the description in order tofacilitate understanding of the invention, but these numerical valuesare merely examples, and any appropriate values may be used, unlessotherwise indicated. Divisions of the described items in the abovedescription are not essential to the present invention. Depending onnecessity, subject matter described in two or more described items maybe combined and used, and subject matter described in a described itemmay be applied to subject matter described in another described item(unless contradicted). A boundary of a functional component or aprocessor in the functional block diagrams may not necessarilycorrespond to a boundary of a physical part. An operation by a pluralityof functional components may be physically executed by a single part, oran operation of a single functional component may be physically executedby a plurality of parts. In the sequence charts described in theembodiment, the order can be changed reversely, unless those arecontradicted. For the convenience of description, the base stationapparatus 100 and the user device 200 are described by using thefunctional block diagrams; however, such devices may be implemented inhardware, software, or combinations thereof. The software to be operatedby the processor included in the base station apparatus 100 inaccordance with the embodiment of the present invention, and thesoftware to be operated by the processor included in the user device 200in accordance with the embodiment of the present invention may berespectively stored in any appropriate storage medium, such as a randomaccess memory (RAM), flash memory, read-only memory (ROM), EPROM,EEPROM, register, hard disk drive (HDD), removable disk, CD-ROM,database, server and the like.

Notification of information is not limited to the aspects/embodimentdescribed in this specification, and may be given by any other methods.For example, the notification of information may be performed byphysical layer signaling (for example, Downlink Control Information(DCI), Uplink Control Information (UCI)), higher layer signaling (forexample, Radio Resource Control (RRC) signaling, Medium Access Control(MAC) signaling, broadcast information (Master Information Block (MIB),System Information Block (SIB))), or other signals, or a combinationthereof. Further, the RRC signaling may be referred to as an RRC messageand may be, for example, an RRC Connection Setup message, an RRCConnection Reconfiguration message, or the like.

Each of aspects/embodiment described in the present specification may beapplied to LTE (Long Term Evolution), LTE-A (LIE-Advanced), SUPER 3G,IMT-Advanced, 4G, 5G, FRA (Future Radio Access), W-CDMA (registeredtrademark), GSM (registered trademark), CDMA 2000, UMB (Ultra MobileBroadband), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, UWB(Ultra-WideBand), Bluetooth (registered trademark), a system using otherappropriate systems, and/or a next generation system expanded based onthese systems.

The processing procedures, the sequences, the flowcharts and the like ofthe respective aspects/embodiment described in this specification may bereversed in order unless there is a contradiction. For example, themethod described in this specification presents elements of varioussteps in an exemplary order and is not limited to a presented specificorder.

A specific operation disclosed to be performed in the base stationapparatus 100 in the present specification may be performed in an uppernode in some cases. In a network composed of one or plurality of networknodes having the base station apparatus 100, it is apparent that variousoperations that are performed for communication with the user device 200can be performed by the base station apparatus 100 and/or anothernetwork node different from the base station apparatus 100 (e.g. MME orS-GW, though not limited thereto). Although the case where anothernetwork node different from the base station apparatus 100 is single isdescribed in the example above, a combination of a plurality of othernetwork nodes (e.g. MME and S-GW) may be used.

The respective aspects/embodiment disclosed in the present specificationcan be used singly, used in combination, and used by switching inoperation.

The user device 200 can be also referred to by those skilled in the artas a subscriber station, a mobile unit, a subscriber unit, a wirelessunit, a remote unit, a mobile device, a wireless device, a wirelesscommunication device, a remote device, a mobile subscriber station, anaccess terminal, a mobile terminal, a wireless terminal, a remoteterminal, a handset, a user agent, a mobile client, a client or severalother appropriate terms.

The base station apparatus 100 may be referred to by those skilled inthe art as NB (NodeB), eNB (evolved node), gNB, base station (BaseStation) or several other appropriate terms.

The terms “determining” and “determining” used in this specification mayinclude a wide variety of actions. For example, “determining” and“determining” may include events in which events such as judging,calculating, computing, processing, deriving, investigating, looking up(for example, looking up in a table, a database, or another datastructure), or ascertaining are regarded as “determining” or“determining.” Further, “determining” and “determining” may includeevents in which events such as receiving (for example, receivinginformation), transmitting (for example, transmitting information),input, output, or accessing (for example, accessing data in a memory)are regarded as “determining” or “determining.” Further, “determining”and “determining” may include events in which events such as resolving,selecting, choosing, establishing, or comparing are regarded as“determining” or “determining.” In other words, “determining” and“determining” may include events in which a certain operation isregarded as “determining” or “determining.”

As used in the present specification, the phrase “based on” does notmean “based only on” unless explicitly stated otherwise. In other words,the phrase “based on” means both “based only on” and “based on atleast”.

As long as the terms “including”, “comprising”, and variations thereofare used in the specification or claims, these terms are intended to beinclusive similar to the term “comprising”. Furthermore, it is intendedthat the term “or” used in the specification or claims is not an“exclusive OR”.

In the entirety of the present disclosure, if an article is added bytranslation, for example a, an and the in English, the elements withthose articles can encompass a plurality of elements, unless otherwiseindicated apparently in the context.

It is noted in the embodiment of the present invention that the initialaccess control unit 240 is one example of the control unit. The initialaccess configuration unit 140 is one example of the configuration unit.The PDCCH common search space is one example of the search space. Thetransmission unit 210 or the reception unit 220 is one example of thecommunication unit.

Although the present invention is described in detail heretofore, it isapparent to those skilled in the art that the present invention is notlimited to the embodiment described in this specification. The presentinvention can be implemented as a modified and changed form withoutdeviating from the spirit and scope of the present invention defined bythe claims. Accordingly, the description of the present specification isgiven solely by way of illustration and does not have any restrictivemeaning to the present invention.

REFERENCE SIGNS LIST

-   100 base station apparatus-   110 transmission unit-   120 reception unit-   130 configuration information management unit-   140 initial access configuration unit-   200 user device-   210 transmission unit-   220 reception unit-   230 configuration information management unit-   240 initial access control unit-   1001 processor-   1002 storage device-   1003 auxiliary storage device-   1004 communication device-   1005 input device-   1006 output device

1. A terminal comprising: a processor, coupled to a transceiver, thatmonitors a PDCCH (Physical downlink control channel) candidate in afirst search space during a random access procedure, wherein thetransceiver receives a random access response or a PDSCH (Physicaldownlink shared channel) for contention resolution from a base station,based on information included in the PDCCH candidate, and wherein thetransceiver receives a PDSCH or transmits an uplink signal based oninformation included in a PDCCH candidate monitored in the first searchspace, until a second search space of a type other than the first searchspace is configured after the random access procedure is completed. 2.The terminal as claimed in claim 1, wherein the processor starts tomonitor the first search space from a time point of starting a windowfor receiving the random access response or a time point of starting tomonitor a PDCCH candidate, and wherein the processor uses a PDCCHcandidate including CRC (Cyclic redundancy check) scrambled by RA-RNTI(Random Access-Radio Network Temporary Identifier) for receiving therandom access response.
 3. The terminal as claimed in claim 1, whereinthe processor terminates monitoring the first search space at a timepoint of having the second search space configured.
 4. A base stationapparatus comprising: a transceiver, coupled to a processor, thattransmits, to a terminal, a downlink signal configured with a PDCCH(Physical downlink control channel) candidate in a first search spaceduring a random access procedure, wherein the transceiver transmits arandom access response or a PDSCH (Physical downlink shared channel) forcontention resolution to the terminal, based on information included inthe PDCCH candidate, and wherein the transceiver transmits a PDSCH orreceives an uplink signal based on information included in a PDCCHcandidate monitored in the first search space, until the processorconfigures a second search space of a type other than the first searchspace to the terminal after the random access procedure is completed. 5.A communicating method comprising: monitoring, by a terminal, a PDCCH(Physical downlink control channel) candidate in a first search spaceduring a random access procedure; receiving, by the terminal, a randomaccess response or a PDSCH (Physical downlink shared channel) forcontention resolution from a base station apparatus, based oninformation included in the PDCCH candidate; and the monitoring includesreceiving a PDSCH or transmitting an uplink signal based on informationincluded in a PDCCH candidate monitored in the first search space, untila second search space of a type other than the first search space isconfigured after the random access procedure is completed.
 6. Anapparatus comprising: a processor, coupled to a transceiver, thatmonitors a PDCCH (Physical downlink control channel) candidate in afirst search space during a random access procedure; and an input unitthat receives an input, wherein the transceiver receives a random accessresponse or a PDSCH (Physical downlink shared channel) for contentionresolution from a base station, based on information included in thePDCCH candidate, and wherein the transceiver receives a PDSCH ortransmits an uplink signal based on information included in a PDCCHcandidate monitored in the first search space, until a second searchspace of a type other than the first search space is configured afterthe random access procedure is completed.